scsi: iscsi: Get ref to conn during reset handling

The comment in iscsi_eh_session_reset is wrong and we don't wait for the
EH to complete before tearing down the conn. This has us get a ref to the
conn when we are not holding the eh_mutex/frwd_lock so it does not get
freed from under us.

Link: https://lore.kernel.org/r/20210525181821.7617-13-michael.christie@oracle.com
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libiscsi.c

@@ -2492,7 +2492,6 @@ int iscsi_eh_session_reset(struct scsi_cmnd *sc)
 
 	cls_session = starget_to_session(scsi_target(sc->device));
 	session = cls_session->dd_data;
-	conn = session->leadconn;
 
 	mutex_lock(&session->eh_mutex);
 	spin_lock_bh(&session->frwd_lock);
@@ -2507,13 +2506,14 @@ failed:
 		return FAILED;
 	}
 
+	conn = session->leadconn;
+	iscsi_get_conn(conn->cls_conn);
+
 	spin_unlock_bh(&session->frwd_lock);
 	mutex_unlock(&session->eh_mutex);
-	/*
-	 * we drop the lock here but the leadconn cannot be destoyed while
-	 * we are in the scsi eh
-	 */
+
 	iscsi_conn_failure(conn, ISCSI_ERR_SCSI_EH_SESSION_RST);
+	iscsi_put_conn(conn->cls_conn);
 
 	ISCSI_DBG_EH(session, "wait for relogin\n");
 	wait_event_interruptible(conn->ehwait,